Vegetated treatment area (VTAs) efficiences for E. coli and nutrient removal on small-scale swine operations

Authors: Harmel, Daren; PAMPELL, R - Texas Agrilife Research; GENTRY, T - Texas A&M University; Smith, Douglas; Hajda, Chad; WAGNER, K - Oklahoma State University; SMITH, P - Texas A&M University; Haney, Richard; HIGGS, K - Former ARS Employee

Submitted to: International Soil and Water Conservation Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2018
Publication Date: 2/12/2018
Citation: Harmel, R.D., Pampell, R., Gentry, T., Smith, D.R., Hajda, C.B., Wagner, K., Smith, P.K., Haney, R.L., Higgs, K.D. 2018. Vegetated treatment area (VTAs) efficiences for E. coli and nutrient removal on small-scale swine operations. International Soil and Water Conservation Research. 6(2):153-164. https://doi.org/10.1016/j.iswcr.2018.02.002.
DOI: https://doi.org/10.1016/j.iswcr.2018.02.002

Interpretive Summary: As small-scale animal feeding operations work to manage their byproducts and avoid regulation, they need practical, cost-effective methods to reduce environmental impact. One such option is using vegetative treatment areas (VTAs) with permanent grass cover to treat runoff; however, research is limited on VTA effectiveness as a waste management alternative for smaller operations. This study evaluated the efficiencies of VTAs in reducing bacteria and nutrient runoff from small-scale swine operations in three counties in Central Texas. Based on 4 yr of runoff data, the Bell and Brazos VTAs significantly reduced loads and concentrations of bacteria and nutrients (except NO3-N) and had treatment efficiencies of 73-94%. Most notably, the Bell VTA reduced loads of bacteria, nitrogen, and phosphorus similar to that of the background (control). In spite of significant reductions, runoff from the Brazos VTA had higher concentrations and loads than the control site, especially following installation of concrete pens and increased pen washing, which produced standing water and increased bacteria and nutrient influx. The Robertson VTA produced fewer significant reductions and had lower treatment efficiencies (29-69%); however, bacteria and nutrient concentrations and loads leaving this VTA were much lower than observed at the Bell and Brazos County sites due to alternative solids management and enclosed pens. Based on these results and previous research, VTAs can be practical, effective waste management alternatives for reducing nutrient and bacteria losses from small-scale animal operations, if properly designed and managed. This includes: establishing grass vegetation that remains actively growing year round, harvesting hay to remove nutrients, using VTA area/animal ratio (along with the VTA area/source area ratio) to determine VTA size, implementing solids pre-treatment/removal with the VTA (particularly in sensitive areas), and conducting regular maintenance to prevent standing water and distribute flow across the entire VTA width.

Technical Abstract: As small-scale animal feeding operations work to manage their byproducts and avoid regulation, they need practical, cost-effective methods to reduce environmental impact. One such option is using vegetative treatment areas (VTAs) with perennial grasses to treat runoff; however, research is limited on VTA effectiveness as a waste management alternative for smaller operations. This study evaluated the efficiencies of VTAs in reducing bacteria and nutrient runoff from small-scale swine operations in three counties in Central Texas. Based on 4 yr of runoff data, the Bell and Brazos VTAs significantly reduced loads and concentrations of E. coli and nutrients (except NO3-N) and had treatment efficiencies of 73-94%. Most notably, the Bell VTA reduced loads of E. coli, NH4-N, PO4-P, total N, and total P similar to that of the background (control). In spite of significant reductions, runoff from the Brazos VTA had higher concentrations and loads than the control site, especially following installation of concrete pens and increased pen washing, which produced standing water and increased E. coli and nutrient influx. The Robertson VTA produced fewer significant reductions and had lower treatment efficiencies (29-69%); however, E. coli and nutrient concentrations and loads leaving this VTA were much lower than observed at the Bell and Brazos County sites due to alternative solids management and enclosed pens. Based on these results and previous research, VTAs can be practical, effective waste management alternatives for reducing nutrient and bacteria losses from small-scale animal operations, if properly designed and managed. This includes: establishing grass vegetation that remains actively growing year round, harvesting hay to remove nutrients, using VTA area/animal ratio (along with the VTA area/source area ratio) to determine VTA size, implementing solids pre-treatment/removal with the VTA (particularly in sensitive areas), and conducting regular maintenance to prevent standing water and distribute flow across the entire VTA width.